1. Field of the Invention
The present invention relates generally to self-loading and unloading material handling devices adapted for attachment to a vehicle for transportation of a bale of material. More particularly, the lifting device hereof provides an improved structure for selectively engaging, lifting, and transporting a round bale of material.
2. Description of the Prior Art
Presently, in the field of self-loading and unloading material handling devices, round bales of material, such as hay, are lifted for transportation to a use site. The bales are generally cylindrical in shape, and are relatively large and heavy. For example, a typical bale may be up to about six feet in both length land diameter, and weigh up to about 1500 pounds or more. As a result, special equipment must be employed to lift the bales for transportation.
In the past, dedicated bale handlers have been provided for lifting bales for transportation. Examples of such dedicated handlers are described in U.S. Pat. No. 3,877,595 to Edelman, and U.S. Pat. No. 4,053,069 to Love. These references disclose bale lifting trailers configured for attachment to a towing vehicle. The lifting trailers each include a pair of clamping arms pivotally coupled with a rotatable axle. The clamping arms are configured for movement between an open position, and a closed position. A linkage cable intercouples the clamping arms. A winch cable is attached at a midpoint of the linkage cable, and is configured to pull on the linkage cable to close the clamping arms and to lift the bale. Once the bale has been lifted, the towing vehicle is able to transport the bale to a use site where the bale is lowered and placed on the ground.
Such lifting trailers, however, present several problems. For example, such trailers are dedicated solely to the purpose of lifting bales. Lifting trailers are also often relatively lightweight, and are susceptible to early wear.
Systems have also been developed which are designed to be permanently attached to a vehicle, such as a flat bed truck. These vehicle-mounted systems generally include a pair of clamping arms which are pivotally coupled with a structure. The clamping arms are configured for movement between open and closed positions. The structure is mounted to a bed of a vehicle, and is configured for rotation to move the clamping arms between lowered and raised positions.
A pair of clamping arm cylinder assemblies is provided for moving the arms between the closed and open positions for engaging and disengaging a bale, respectively. In addition, a main cylinder assembly is provided for rotating the structure and moving the clamping arms between the lowered and raised positions for lowering and raising the bale, respectively. Such a system, however, is relatively expensive, and requires a heavy duty cylinder assembly for operation. Therefore, a significant, and heretofore unsolved, need exists to provide a lifting device for lifting bales of material having improved bale-handling characteristics, and having a relatively improved and more durable structure.